Process and apparatus for manufacture of a thermoplastic yarn with residual twist

ABSTRACT

Process and apparatus for texturizing a thermoplastic yarn to provide a residual twist couple by generating a twist in the yarn as the yarn is unwound and contacting the twisted yarn with a twist barrier ring downstream from a heating element and upstream from a ring and traveller spindle windup system.

United States Patent [1 1 UNITED STATES PATENTS 7/1972 Rothwell et a1 57/34 HS X Buzano Dec. 11, 1973 PROCESS AND APPARATUS FOR 2,572,135 10/1951 Gonsalves 57 106 x MANUFACTURE OF A THERMOPLASTIC 6 3 ei/6:65 6 5 4 11;

, ar er e a YARN WITH RESIDUAL TWIST 2,788,634 4/1957 Grouzet 57/106 [75] Inventor: Michel Buzano, Villeurbanne, 3,581,487 6/1971 Loomes et a1. 5 4 HS France 3,449,900 6/1969 Eldridge et a1. 57/106 x 3,727,394 4/1973 Grieve 57/75 X Asslgneei Societe Rhodiaceta, Paris, France 3,084,500 4/1963 Recher 57/75 x [22] Filed: Oct. 11, 1971 0 BIG P EN S O A LIC TI S F R N AT T R PP A ON [211 App! 19mm 299,031 5/1928 Great Britain 57/60 Related US. Application Data 777,625 6/1957 Great Britain 6. 57/34 HS [63] Continuation-impart of Ser. No. 95,013, Dec. 4,

1970. Primary ExaminerDonald E. Watkins 30 Foreign Application Priority Data Att0rneyLeonard W. Sherman 8t 81.

Oct. 22, 1970 France 7038481 4 Dec. 12, 1969 France 6943178 [57] ABSTRACT [52] US. Cl. 57/34 HS, 57/157 TS, 57/75 Ill. Cl. Process and apparatus for texturizing a the mgplastic Field of Search 34 34 yarn to provide a residual twist couple by generating a 63, 75, 106, twist in the yarn as the yarn is unwound and contact- 157 157 MS, 157 T3 ing the twisted yarn with a twist barrier ring downstream from a heating element and upstream from a References Clted ring and traveller spindle windup system.

9 Claims, 10 Drawing Figures PATENTED DEC 1 1 M5 SHEET 3 [IF 3 PROCESS AND APPARATUS FOR MANUFACTURE OF A THERMOPLASTIC YARN WITH RESIDUAL TWIST The present invention is a continuation-in-part of copending U. S. Patent application Serial Number 95,013 filed Dec. 4, 1970.

BACKGROUND OF THE INVENTION 1. Field of Invention The present invention pertains to a process and an apparatus for the manufacture of a texturized textile yarn with residual twist and, more particularly, to such process and apparatus with a twist generated upstream of a twist barrier ring.

2. Discussion of the Prior Art Yarns with a residual twist are particularly used in the manufacture of stockings, knitting alternately a row of yarn with an S residual twist and a row of yarn with a Z residual twist. In this way, with yarns of substantially zero inherent elasticity, an extremely elastic knitted fabric can be obtained.

It is known that yarns with residual twist can be obtained at high speed by false twisting, particularly by pneumatic false twisting; however, in the latter case the consumption of air imposes a limit on production rates. Furthermore, the reproducibility of the effects is difficult to control.

It has also been proposed to obtain residual twist yarns by driving back or accumulation of twist. Driving back of twist is obtained by combining and then separating several ends of yarn. However, the operation of separation is difficult to carry out and requires complicated apparatus.

A process has also been proposed for impacting elasticity to a yarn by withdrawing yarn from a crosswound package and guiding it over a heating element, then across a twist barrier towards a ring and traveller twisting spindle. In this way the accumulated twist is a little higher than that given by the ring and traveller twisting spindle, however, the springiness of the yarn is not as great as is desired.

In order to deal with this difficulty, a process has been proposed in which the temporary accumulated twist from a traveller is set in a zone to which it can freely run back. However, in this case, the traveller is always used as the twist barrier, and if correct values of the residual twist are to be obtained, considerable balloon tensions are necessary. A method of obtaining such a result utilizes a traveller of special shape provided with an acute peak. In general, however, it is not desirable to have excessively high balloon tensions. Moreover, the sliding of a traveller on a ring is a phenomenon which is difficult to control, the traveller having a tendency to advance in jumps. The traveller further tends to vibrate and consequently differences in twist accumulation result. Furthermore, if the torsion is required to remain constant, the spindle velocity has to decrease as the diameter of the package increases. It is thus necessary to furnish the device with a spindle velocity control system. Finally, the linear velocity of the traveller cannot exceed a certain value and is a limiting factor, which in turn requires a limitation of the spindle velocity and the velocity of the material.

It has also been proposed to cause an accumulation of twist on a ring situated upstream of the windup device and downstream of a heating element into which the twist runs back freely. But in this case, although the traveller vibrations have little disturbing effect on the accumulation of twist, which is an advantage, there is still a dependence on the spindle as the torsion generating element, which is a disadvantage.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a process and apparatus for providing a yarn withresidual twist couple.

The present invention is generally characterized in a process for texturizing a yarn of thermoplastic material by generating a twist in the yarn and feeding the yarn in contact with a twist barrier ring disposed upstream of a ring and traveller windup device, the twist being set upstream of the twist barrier ring. The present invention is further generally characterized in apparatus for texturizing a yarn of thermoplastic material including means for unwinding and generating a twist in a yarn carried by a package and a twist barrier ring disposed downstream of a heater and upstream of a windup device for drawing the yarn from the heater in contact with the twist barrier ring.

The present invention has another object in that the twist is generated by the unwinding of a yarn which has been twisted on a continuous twister, for example by pulling a yarn substantially axially from the end of a cop obtained by spinning and winding using a ring and traveller twisting spindle.

Where the yarn is wound up by a system which itself imparts twist to the yarn, it has been observed that the torsion imparted by the twist generator upstream of the twist barrier element has to be greater than the windup torsion for the residual twist to be in the same direction as the twist from the twist generator and thus for the process to be carried out. Accordingly, in the case of a ring and traveller spindle windup system, if N is the rotational velocity of the spindle, d is the diameter of the package, which is taken to be cylindrical, and V is the unwinding velocity, then the sliding of the traveller on the ring causes a windup twist Tr (N/V) (Had). The twist of the unwound yarn equals the true twist: Ty N/ V.

When the yarn is pulled off the end of a package, it is therefore necessary for the twist of the unwound yarn to be greater than the windup twist in order for the process of the invention to be carried out.

Another object of the present invention is to provide apparatus for texturizing a yarn of thermoplastic material, such apparatus including means for unwinding and producing a twist in a yarn carried by a package and delivering it to a heater, a twist barrier and a windup means disposed to draw yarn from the heater in contact with the twist barrier.

A further object of the present invention is to dispose a twist barrier ring downstream of a heater plate onto which the twist runs freely and upstream of a windup device such as a ring and traveller spindle.

Some of the advantages of the present invention are that texturized yarn produced in accordance with the present invention has a residual twist in the direction of unwinding of the yarn from a feed cop and has a substantially high constant value of residual torque couple regardless of spindle rotational speed, and that the texturization of the yarn has excellent uniformity and regularity.

Other objects and advantages of the present invention will become apparent from the following descrip- 3 tion of the preferred embodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of apparatus for carrying out the process according to the invention.

FIG. 2 is a broken view of the apparatus of FIG. 1 illustrating the path of the yarn in the zone of the twist accumulator ring.

FIGS. 3, 4 and 5 are cross sections of various twist accumulator rings according to the present invention.

FIG. 6 is a diagram of apparatus used for measuring residual twist.

FIG. 7 is'a graph illustrating the effect of spindle velocity on residual twist couple.

FIG. 8 is a graph illustrating the influence of material velocity on residual twist couple.

FIG. 9 is a graph illustrating the influence of the windup tension on residual twist couple.

FIG. 10 is a graph illustrating the influence of ageing on residual twist couple.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the apparatus illustrated in FIG. 1, a yarn 12 is unwound substantially axially from a feed cop 14 by a delivery device 16 and passes over a heating plate 18 to a pigtail 20. The yarn is textured by accumulation of twist on a twist accumulator ring 22 acting as a twist barrier element and mounted on a ring rail 24 upstream of a ring 26 of a windup system having a traveller 28 through which the yarn passes before collection on a windup cop 30.

Feed cop 14 is supported such that axial unwinding of yarn 12 by delivery device 16 generates a twist in yarn 12. Of course, any means for unwinding and generating a twist in yarn 12 as the yarn leaves a package may be utilized with the present invention; however, the axial unwinding of the yarn from fixed feed cop 14 has been found to be advantageous. Furthermore, any suitable twist generator may be used with the present invention, it being of primary importance that the yarn have a twist genetated therein upstream of the heater and twist barrier ring. The twist generated by unwinding from the cop 14 is arrested on the ring 22 and accumulates freely on the heating plate 4. The ring 22 may have a rounded or arcuate inner peripheral configuration 32, such as the profile of ring 22a illustrated in FIG. 3, or may have pointed edges such as 34 on the profile of ring 22b illustrated in FIG. 4 and 36 on the profile of ring 22c illustrated in FIG. 5. The configuration or profile of the inner periphery of ring 22a is smoothly convex whereas the inner peripheral configurations of rings 22b and 22c have protruding pointed edges 34 and 36, respectively, with edge 34 of ring 22b being centrally disposed to include an angle greater than 90 and edge 36 of ring 22c being offset to include an angle of approximately 90. In practice, it has been observed that the shapes of the embodiments illustrated in FIGS. 4 and 5 provide better accumulation of twist and better results.

The process and apparatus of the present invention will be described with reference to the following specific examples; however, it is understood that the following examples are presented for purposes of illustration only and the present invention is not meant to be limited thereto.

The following examples illustrate the advantages of the present invention in which a twist generator is disposed upstream of a twist barrier element as compared with known processes using a twist generator disposed downstream of a twist barrier element.

As above mentioned, the true twist T of the feed should be greater than T but it has been seen that T depends on 1/1111. d is not rigorously constant, since the diameter of the windup cop varies. In fact, however, the accumulation of twist depends on the blocking of the twist, and it is sufiicient that the twist of the unwound yarn remains greater than the windup twist.

EXAMPLE 1 Spindle velocity 7300 rpm. Material velocity 700 m/min Mean package diameter 0.047 m.

The following table summarizes the direction of the twist:

Unwinding Windup Direction of direction from direction onto residual feed cop l4 windup cop 30 twist Z Z Z Z 5 Z S S S S Z S It can be seen that the direction of the residual twist is that of the direction of unwinding from the feed cop.

(2) An identical yarn is treated under the same conditions but comes from a zero-twist spinning bobbin.

The following table summarizes the direction of the twist:

Direction Unwinding Windup direction of residual direction onto windup cop 30 twist couple S S S S Z Z Z Z Z EXAMPLE 2 This example is intended to show the effect of the spindle velocity on the residual twist couple.

The yarn treated is one of polyhexamethylene adipamide (polyamide 6.6) 22 dtex/2 filaments.

An apparatus according to FIG. 1 is used, provided with a twist barrier ring 22b acting as a twist barrier and having a profile as in FIG. 4.

For comparison, an identical'yarn is treated under the same operating conditions, but in a first case on an apparatus with no twist barrier ring, so that the traveller of the windup device constitutes the twist barrier. The yarn obtained will be called Control 1 below. In a second case the yarn is treated on an apparatus provided with a twist barrier ring and a supply bobbin of the spinning bobbin type from which yarn is withdrawn with only a very low induced twist so that the twist generator is constituted by the windup system. The yarn obtained will be called Control 2 below.

The yarn according to the invention and the yarn according to Control I was obtained by spinning and winding up on a cop with a ring and traveller twisting spindle system. The spinning rate was 500 m/min, and the spindle velocity was 7,500 r.p.m. The yarn according to Control 2 was wound up on a so-called zero twist system.

In the three cases the yarn is treated under the following operating conditions:

Texturizing 700 m/min. Balloon tension 7 g Temperature 250C The residual twist is measured in the following manner with reference to FIG. 6:

A length of yarn is unwound and one end is attached to a fixed point A. The yarn is passed through a hook whose weight equals 0.0060 g/tex at a point B situated 80 cm below point A, and the other end of the yarn is fixed to point A.

The yarn is released by removing the hook situated at B. Under the effect of the residual twist, the yarn starts to twist round. Using'a twist meter of any known type, the binding twist between the two ends of the yarn is counted.

The results obtained are summarized in the curves shown in FIG. 7, where the abscissa represents the rotational velocity N of the spindle and the ordinate represents the values of residual twist C Curve C corresponds to the yarn treated according to the method of the invention.

Curve D corresponds to Control 1.

Curve E corresponds to Control 2.

It can be noticed on Curve D that the value of the residual twist continuously increases up to a rotational speed of the spindle equal to 9,500 r.p.m.; then, this value decreases before increasing again. Now it is I known that a traveller should not be used for linear velocities exceeding a given value, beyond which the traveller begins to vibrate and allows the twist to escape in an uncontrolled manner. This limiting value in the present case corresponds to a rotational velocity of the spindle equal to 9,500 r.p.m. The break in the curve is thus logicahsince the traveller acts as a twist barrier element.

It can be seen from Curve E that the value of the residual twist is substantially constant, but the values of the residual twist are low.

Finally, on Curve C,.which corresponds to the invention, the value of the residual twist couple remains substantially constant at a high mean value of the order of 800; thus, within experimental error, it can be said that the process of the present invention is independent of the rotational speed of the spindle.

EXAMPLE 3 This example is intended to show the effect of the speed of the material on the residual twist couple.

The yarn treated is the same as in Example 2.

The balloon tension is 7 g, and the temperature of the heating plate is 250.

The ratio: [deliveryrate/spindle velocity] equals 10.

The results obtained are summarized in the curve of FIG. 8, in which the abscissa represents the speed V of the material and the ordinate represents the values of the residual twist C There can be seen in the present case a slight increase of the residual twist C, from 500 to 700 m/min., then a decrease of the value of the residual twist beyond 700 m/min., this being essentially due to an insufficient heat treatment.

EXAMPLE 4 Texturizing rate 700 m/min. Rotational velocity of the spindle 7300 r.p.m. 250C Temperature The variation of the value of the residual twist as a function of the windup tension is shown in FIG. 9, where Curves F, G and H are shown in the same way as in Example 2.

Curve F corresponds to the yarn treated by the process according to the invention.

Curve G corresponds to Control 1.

Curve H corresponds to Control 2.

It can be seen that for the process according to the invention the maximum value of the residual twist is attained for low values of tension, 6 to 8 g, while the maximum is situated at about 11 g for Control 1 and 25 g for Control 2.

The differences between Curves F and G do not appear to be very considerable, but moreover-it has been found that the regularity of the texturizing effect is better when the process according to the invention is used.

EXAMPLES 5 TO 7 These examples illustrate the effect of ageing on the residual twist couple. It is known that in yarns of this type the residual twist couple diminishes rapidly in a first period, then becomes stabilized.

In these examples, the same yarn as before is treated in each case, under the following conditions;

Velocity of material 700 m/min. Spindle velocity 8400 r.p.m. Balloon tension 7 g.

The values of the residual twist behave as shown in Curve I (see FIG. 10), where the number of days is represented along the abscissa and the residual twist couple is represented along the ordinate.

It is seen that the yarn behaves normally. There is a fall in the values of the residual twist in the first week, which is normal, then a stabilization.

For comparison, Curves J and K are given on the same diagram, and correspond to the same velocity of material and to spindle velocities respectively equal to 10,600 r.p.m. and 11,700 r.p.m. It can be seen from these curves that the initial value of the twist couple tends to be higher, while the stabilized value tends to be lower, but the differences are small.

These examples illustrate the value of the present invention, which enables a yarn having a residual twist to be obtained at high speed with a controllable reproducibility of the effect, and with a uniform value of the residual twist.

Inasmuch as the present invention is subject to many variations, modifications and changes in detail, it is intended that all matter described in the specification or shown in the drawings be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A process for texturizing a yarn of thermoplastic material comprising the steps of generating a twist in the yarn; feeding the twisted yarn in contact with a twist barrier ring disposed upstream of a ring and traveller windup device; setting the twist in the yarn upstream of the twist barrier ring; and winding up the yarn with the ring and traveller windup device.

2. A process is recited in claim 1, wherein said twist generating step includes unwinding the yarn substantially axially from a cop wound on a twisting frame, the twist being set between the cop and the twist barrier ring.

3. A process as recited in claim 2 wherein said step of winding up the yarn produces a twist on the yarn downstream of the twist barrier ring, the twist from said generating step upstream of the twist barrier ring being greater than the twist from said winding step downstream of the twist barrier ring.

4. Apparatus for texturizing a yarn of thermoplastic material comprising means for generating a twist in a yarn supplied by a package; means for delivering the twisted yarn to a heater; a twist barrier ring disposed downstream of said heater; and windup means disposed downstream of said twist barrier ring to draw yarn from said heater in contact with said twist barrier ring.

5. The apparatus as recited in claim 4 wherein said twist generating means includes means for generating the twist in the yarn coinciding with unwinding of the yarn from the package.

6. The apparatus as recited in claim 5 wherein said ring has a smoothly rounded inner peripheral configuration in cross section.

7. The apparatus as recited in claim 5 wherein said ring has an inner peripheral configuration with a pointed edge in cross section.

8. Claim 7 wherein said pointed edge includes an angle of greater than 9. Claim 7 wherein said pointed edge includes an angle of substantially 90.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo' 3,777,465 Dated December 11, 1973 Inventor s) MICHEL BUZANO It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Please change the assignment information in the heading to read as follows:

- Assignees; Rhone-Poulenc-Textile, S .A. Paris, France.

Sign! and Scalcd this sixteenth Day of December 1975 [SEAL] Arte! RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of'Parents and Trademarks 

1. A process for texturizing a yarn of thermoplastic material comprising the steps of generating a twist in the yarn; feeding the twisted yarn in contact with a twist barrier ring disposed upstream of a ring and traveller windup device; setting the twist in the yarn upstream of the twist barrier ring; and winding up the yarn with the ring and traveller windup device.
 2. A process is recited in claim 1, wherein said twist generating step includes unwinding the yarn substantially axially from a cop wound on a twisting frame, the twist being set between the cop and the twist barrier ring.
 3. A process as recited in claim 2 wherein said step of winding up the yarn produces a twist on the yarn downstream of the twist barrier ring, the twist from said generating step upstream of the twist barrier ring being greater than the twist from said winding step downstream of the twist barrier ring.
 4. Apparatus for texturizing a yarn of thermoplastic material comprising means for generating a twist in a yarn supplied by a package; means for delivering the twisted yarn to a heater; a twist barrier ring disposed downstream of said heater; and windup means disposed downstream of said twist barrier ring to draw yarn from said heater in contact with said twist barrier ring.
 5. The apparatus as recited in claim 4 wherein said twist generating means includes means for generating the twist in the yarn coinciding with unwinding of the yarn from the package.
 6. The apparatus as recited in claim 5 wherein said ring has a smoothly rounded inner peripheral configuration in cross section.
 7. The apparatus as recited in claim 5 wherein said ring has an inner peripheral configuration with a pointed edge in cross section.
 8. Claim 7 wherein said pointed edge includes an angle of greater than 90*.
 9. Claim 7 wherein said pointed edge includes an angle of substantially 90*. 